Mixing PFAS and microplastics increases toxicity, new study claims

A new study has revealed that perfluoroalkyl substances (PFAS) and PET microplastics are more toxic (to freshwater species, at least) when combined.

Focusing on water fleas (Daphnia magna), a sentinel species in freshwater ecologies, the study highlights alarming developmental and reproductive impairments. 

In particular, the researchers highlighted the compounding effect of exposure, whereby fleas with historic exposure experienced multiplied impacts. 

Maldevelopment, synergistic toxicity, compounding impacts 

The study demonstrated exposure to PFAS and microplastics mixtures delayed sexual maturity, stunted growth, and reduced fecundity in Daphnia. 

Approximately 41% of effects were judged to be synergistic, likely stemming from interactions between the negatively-charged microplastics and PFAS that enhanced retained uptake. 

Daphnia with a history of exposure to pollution exhibited reduced resilience to chemical mixtures compared to naïve populations. 

Why PFAS and microplastics uniquely impact freshwater ecosystems 

Both PFAS and microplastics are environmentally persistent and bioaccumulate, wreaking havoc in freshwater contaminated by waste streams.  

PFAS disrupt endocrine functions in freshwater species, impair reproduction, cause developmental abnormalities, weaken immunity, and increase mortality. 

Microplastics, when ingested by microorganisms, block digestive systems and in water, leach endocrine disruptors, like bisphenols, brominated flame retardants and phthalates. 

Regulating mixtures as well as individual pollutants 

The findings of the study underscore the critical need to regulate chemical mixtures rather than simply assessing pollutants in isolation.  

Further, PFAS and microplastics frequently co-occur in natural environments, such that their actual impacts (and therefore, their regulatory priority) are probably underestimated. 

For instance, while they are regulated in drinking water at specific limit, if their synergistic toxicity is ignored, compliant levels may actually be unsafe.